Association Study Between Schizophrenia And Gene Polymorphisms Of Methl-CpG-binding Protein Family

Association study between schizophrenia and gene polymorphisms of methyl-CpG-binding protein familySchizophrenia is the most common and serious mental disease, the burden of disease is very heavy. Until now, the pathogenesis of schizophrenia remains unknown. Most studies found that genetic factor may be played a major role in schizophrenia. The specific susceptibility genes associated with schizophrenia remains unidentified.ObjectiveThe purpose of this study is to identify the genetic association between the polymorphisms of methyl-CpG-binding protein (MBD) family genes and schizophrenia by using the protocols in molecular biology, genetic epidemiology and biostatistics, and to analyze the effect of gene-gene interaction. The results obtained in this study will provide technical support to clarify the inheritance of schizophrenia, and provide supporting evidence to understand the role of epigenetic mechanisms in the pathogenesis of schizophrenia.Methods200 family trios consisted of father, mother, and affected offspring with schizophrenia were collected for MBD genetic analysis.10 tag SNPs were chosen on MBD family genes including rs125555,rs140689, rs140687 and rs140686 on MBD1 gene, rs3786254,rs7614 and rs1145317 on MBD2 gene, rs7252741, rs4807934 and rs4807122 on MBD3 gene. Ten tag SNPs were genotyped using PCR-based ligase detection reaction analysis. The genotype frequency of each tag SNPs distribution was tested for Hardy-Weinberg equilibrium. The HHRR test and TDT test were used to detect the allelic association between tag SNPs of MBD gene and schizophrenia. Haplotype analysis and Linkage disequilibrium analysis was using Pedigree based association test (PBAT) software. The association between tag SNPs of MBD genes and clinical symptoms and type of schizophrenia was used byχ2 test. To elucidate the clinical heterogeneity and genetic heterogeneity based on clinical subgroups analyzed. The relationship between gene-gene interaction and schizophrenia was analyzed by Pedigree-based generalized multifactor dimensionality reduction (PGMDR) software.Results(1)H-W testThe genotype frequency distributions of each tag SNPs in patient group and parent group were not deviated from the H-W equilibrium, thus each SNP could used as genetic markers to test the relationship between MBD genes and schizophrenia.(2) HHRR testIn total samples, HHRR test showed that MBD2 gene rs1145317 allele frequency distribution was statistically significant difference in case and control group (χ2= 5.348, P=0.021). This result indicates that the rs1145317 locus associated with schizophrenia.In the male patient group, MBD2 gene of rs1145317, rs7614 and rs3786254 allele frequency distribution were statistically significant difference in case and control group (χ2=7.400, P=0.007;χ2=4.723, P=0.030;χ2= 4.247, P=0.039), show that the MBD2 gene of rs1145317. rs7614 and rs3786254 associated with schizophrenia in the male patients group.In the female patient group. MBD3 gene rs4807934 allele was statistically significant difference in case and control group (χ2= 4.832. P= 0.028). show that the rs4807934 locus associated with schizophrenia in the female patients group.(3) TDT testIn total samples, TDT analysis showed that the probability of the two different alleles in MBD2 gene rs1145317 deviated from 50% from heterozygous parents (P<0.05). G-allele was passed too much to the patient. This result indicates that the rs1145317 locus associated with schizophrenia.In the male patient group, the probability of the two different alleles in MBD2 gene rs1145317, rs7614 and rs3786254 deviated from 50% from heterozygous parents (χ2=6.420,P=0.011;χ2=4.853,P=0.028:χ2=4.033,P=0.045). G-allele on rs1145317 was passed too much to the patient. A-allele on rs7614 was passed too much to the patient. G-allele on rs3786254 was passed too much to the patient. This result indicates that the rs1145317. rs7614 and rs3786254 locus associated with schizophrenia in the male patients group.In the female patient group, the probability of the two different alleles in MBD3 gene rs4807934 deviated from 50% from heterozygous parents (χ2=4.378,P=0.036). C-allele on rs4807934 was passed too much to the patient. This result indicates that the rs4807934 locus associated with schizophrenia in the female patients group.(4) Haplotype testThere was no haplotypic association for the six haplotype system in the MBD1 gene. There was no haplotypic association for the haplotype system of rs3786254-rs7614 and rs3786254-rs7614-rs1145317 in the MBD2 gene. There was no haplotypic association for the three haplotype system in the MBD3 gene. The result indicates that these haplotype system were not associated with schizophrenia. The haplotype system of rs7614-rs 1145317 frequency distribution were statistically significant difference in case and control group (P=0.029). This result indicates that the haplotype system of rs7614-rs1145317 associated with schizophrenia.(5) Analysis for gene-gene interactionThe PGMDR method identified that the best model of rs4087122/rs4807934 to analyze the gene-gene interaction of schizophrenia. Person who carries rs4807122CC or rs4807934AA genotypes and rs4807122CT or rs4807934AG genotypes of MBD3 gene at the same time will have more risk to affect the disease. The risks were 2.114 and 2.553 times respectively compared to the person who carries rs4807122TT genotype and rs4807934GG genotype (95%CI:1.125-3.971, P<0.05 95%CI:1.071～6.085, P<0.05).(6) Analysis for clinical symptomsIn total samples, rs140687 and rs140689 on MBD1 gene; rs1145317 and on MBD2 gene; rs7252741, rs4807934 and rs4807122 on MBD3 gene were associated with some positive symptoms of schizophrenia.In the male patient group, rs125555,rs140686 and rs140687 on MBD1 gene; rs7614, rs1145317 and rs3786254 on MBD2 gene; rs7252741 and rs4807934 on MBD3 gene were associated with some positive symptoms of schizophrenia. The rs1145317 on MBD2 gene was associated with premorbid personality of schizophrenia.In the female patient group, rs140686,rs140689 and rsl25555 on MBD1 gene; rs7614,rs3786254 and rs1145317 on MBD2 gene; rs4807122 and rs7252741 on MBD3 gene were associated with some positive symptoms of schizophrenia.(7) Analysis for clinical typeIn total samples, the tag SNPs of MBD1 and MBD2 gene were not associated with paranoid and undifferentiated schizophrenia. The rs7252741 of MBD3 gene was associated with paranoid schizophrenia. The tag SNPs of MBD3 gene were not associated with undifferentiated schizophrenia.In the male patient group, the rs1145317 and rs3786254 of MBD2 gene were associated with male paranoid schizophrenia. The rs7252741 of MBD2 gene was associated with male paranoid schizophrenia.In the female patient group, the rs4807122 of MBD3 gene was associated with female undifferentiated schizophrenia.ConclusionsAccording to the results, we have obtain the following conclusions:①MBD2 gene rs1145317 locus was associated with schizophrenia;②rs1145317,rs7614,rs3786254 loci of MBD2 gene were associated with male schizophrenia; MBD3 gene rs48079334 locus was associated with female schizophrenia;③The haplotype system of rs7614-rsl 145317 associated with schizophrenia;④The best model to analyze the gene-gene interaction of schizophrenia was rs4087122/rs4807934. Person who carries rs4807122CC or rs4807934AA genotypes and rs4807122CT or rs4807934AG genotypes of MBD3 gene at the same time will have more risk to affect the disease;⑤There are many SNPs in the MBD genes, which associate with the schizophrenic clinical symptoms. The female schizophrenia has more symptoms of delusion of being loved, bizarre behavior, affective flattening and other delusions;⑥There are many SNPs in the MBD2 and MBD3 gene, which associate with the schizophrenic clinical types;⑦We found the genetic of MBD gene in schizophrenia has gender difference, and the inheritance of schizophrenia has clinical heterogeneity and genetic heterogeneity. In sum, we found the MBD genes were associated with schizophrenia. The results support the polygenic theory of complex disease. At the same time, these results prove that schizophrenia has the clinical heterogeneity and genetic heterogeneity.